The invention includes embodiments that relate to a method of making an organic light-emitting device. The invention also includes embodiments that relate to an organic light-emitting device.
An organic light-emitting device (OLED) is typically a thin film structure formed on a substrate such as glass or transparent plastic. A light-emitting layer (emissive layer) of an organic electroluminescent material and optional adjacent semiconductor layers are sandwiched between a cathode and an anode to form a multi-layered device. The semiconductor layers may be either hole (positive charge)—injecting or electron (negative charge)—injecting layers and also comprise organic materials. The light emitting organic layer may itself consist of multiple sublayers, each comprising a different organic electroluminescent material. Upon application of an appropriate voltage to the OLED, the injected positive and negative charges recombine in the emissive layer to produce light.
The fabrication of a multilayered device comprising organic materials has been problematic using methods involving solvents. This is because of dissolution of underlying layers in solutions employed for disposing the succeeding layers. Further, even if the coating compositions do not dissolve the underlying layer, it is often difficult to achieve continuous and coalesced film coverage. Crosslinked organic materials may be used to circumvent this problem. However, organic layers in multilayer organic light emitting devices are typically cross-linked by heating at temperatures above 130 degrees Celsius. In many instances, light emissive materials used in OLEDs cannot be heated to temperatures above 130 degrees Celsius as photoluminescence yield of theses materials may be reduced following such treatment.
Therefore a method of making a multilayered organic light-emitting device having enhanced structural integrity is greatly desired. Moreover, multilayered organic light emitting devices having enhanced structural integrity are also desired.